If $\Delta$ and $\nabla$ represent forward and backward difference operator then find the value of $$\frac\Delta\nabla-\frac\nabla\Delta$$ I know that $\Delta f(x)=f(x+h)-f(x)$ and $\nabla f(x)=f(x)-f(x-h)$.
But what will be $\frac\Delta\nabla f(x)=\frac1\nabla\{f(x+h)-f(x)\}$?
Will someone please help?